Don't fail on ID overlap for 0th offset when 'offset' attribute is used.
Don't fail on ID overlap for 0th offset when 'offset' attribute is used.

TBR=benrg@chromium.org
BUG=none

Review URL: https://chromiumcodereview.appspot.com/11742040
imuse2012/grit-i18n,imuse2012/grit-i18n,camny125/grit-i18n,camny125/grit-i18n